Absorbing nonwoven materials are often used for wiping spills and leakages of all kinds in industrial, service, office and home locations. There are great demands on the properties of nonwoven materials made for wiping purposes. An ideal wiper should be strong, absorbent, abrasion resistant and exhibit low linting. It should further be soft and have a textile touch. Hydroentangled nonwoven materials are often used as wipes because of their absorbent and textile-like properties.
Hydroentangling or spunlacing is a technique introduced during the 1970'ies, see e.g., CA patent no. 841 938. The method involves forming a fiber web which is either drylaid or wetlaid, after which the fibers are entangled by means of very fine water jets under high pressure. Several rows of water jets are directed against the fiber web which is supported by a movable fabric. The entangled fiber web is then dried. The fibers that are used in the material can be synthetic or regenerated staple fibers, e.g., polyester, polyamide, polypropylene, rayon or the like, pulp fibers or mixtures of pulp fibers and staple fibers. Spunlace materials can be produced in high quality to a reasonable cost and have a high absorption capacity. They can, e.g., be used as wiping material for household or industrial use, as disposable materials in medical care and for hygiene purposes etc.
Through e.g., EP-B-0 333 211 and EP-B-0 333 228 it is known to hydroentangle a fiber mixture in which one of the fiber components consists of continuous filaments in the form of meltblown fibers. The base material, i e the fibrous material which is exerted to hydroentangling, either consists of at least two combined preformed fibrous layers where at least one of the layers is composed of meltblown fibers, or of a “coform material” where an essentially homogeneous mixture of meltblown fibers and other fibers is airlaid on a forming fabric.
Through EP-A-0 308 320 it is known to bring together a pre-bonded web of continuous filaments with a separately pre-bonded wetlaid fibrous web containing pulp fibers and staple fibers and hydroentangle together the separately formed fibrous webs to a laminate. In such a material the fibers of the different fibrous webs will not be integrated with each other since the fibers already prior to the hydroentangling are bonded to each other and only have a very limited mobility. The material will show a marked two-sidedness.
WO 99/22059 discloses a method of producing a nonwoven material by hydroentangling a mixture of continuous filaments, natural fibers and/or synthetic staple fibers. A fibrous web of natural fibers and/or synthetic staple fibers is foam-formed and hydroentangled and integrated with the continuous filaments, for example meltblown fibers.
WO 2005/042819 discloses a method of producing a nonwoven material by forming a web of continuous filaments on a forming fabric and applying a wet-formed fiber dispersion containing synthetic staple fibers having a length between 3 and 7 mm, and natural fibers on top of said continuous filaments. The fibrous web is subsequently hydroentangled to form a nonwoven material.
When making a high quality nonwoven material it is essential that a good fiber formation is achieved and maintained throughout the manufacturing process for both the continuous filaments and the wet laid layers. This gives a material with good visual impression and material properties. Wetlaying an aqueous fiber dispersion by means of inclined wire formation, as e.g. disclosed in EP 0 972 873, EP 1 929 080 and EP 0 411 752, uses a low consistency of the fiber dispersion and provides a good fiber formation. With inclined wire formation it is possible to handle both pulp fibers and short cut staple fibers mixed together. However, since the headbox is placed on an inclined wire a sealing is arranged between the headbox and the wire to prevent the fiber dispersion from running in the wrong direction. The seal makes it impossible for a prefabricated web, such as an unbonded filament web, to pass through the headbox.
In addition, wetlaying an aqueous fiber dispersion on top of a web of unbonded filaments will destroy the formation of the unbonded filaments, since the water will move around the filaments. Foam-forming of the fiber dispersion as disclosed in WO 99/22059 may solve this problem. The foam may however cause problems downstream in the process by making filtration of the hydroentangling water more complicated.